Method of making porous fabric



July 4, 1950 H. w. BEALL METHOD OF MAKING POROUS FABRIC Filed July 11, 1946 ATTORNEY Patented July 4, 1950 UNITED STATES PATENT OFFICE 1 Claim.

My invention relates to a new and useful porous fabric and method of producing the same and involves the step of perforating a preformed sheet of plastic material so as to form an elastic, porous material that can be used for stockings, gloves, garments or the like.

In my invention the initial plastic material can be in the form of flat sheets, which when perforated will constitute yard goods such as now used or it may be preformed so as to form a one piece garment such as a glove or a stocking, or it may be preformed in sections of a garment which may be joined by sewing, cementing or fusing together.

In my invention, the front, back, sleeves, trimming, etc., of a waist, for instance, may be preformed, perforated and then joined together in various ways.

Gloves and like articles can be dipped on a form to a predetermined shape, then ornamentation can be applied as by stamping, or may be sprayed on or applied by numerous other methods, both in the same or different colors, after which the article is perforated.

In making stockings or the like a. form is dipped in a plastic solution which is allowed to harden wholly or in part, then reinforced heel, toe and top is applied by partial dipping or spraying, and a simulated seam may be applied to the back either by spraying through a stencil or with a narrow roller.

The perforations can be formed either by piercing with hot or cold punches, which may be in the form of a pattern, or by an electric spark, operating over the surface of the material. Both of these two methods can be used consecutively or simultaneously on the same piece of material.

My invention contemplates the piercing of plastic material by an electric spark-producing means, the operation being performed in a nonconducting fluid such as oil or other non-conducting, non-inflammable material which prevents the combustion of the plastic material and confines the perforation to the portion of the material that is burned or melted by the heat of the electric spark. This spark can be interrupted either mechanically, electrically or by means of oscillating electric currents.

In a preferred method of making a shirt or other similar article, a plain or embossed metal band is run through a plastic solution to allow a film to form on the band, and an embossing or piercing roller can act on the film to produce a design including indications as to the location of pockets, etc., to produce simulated seams on the film, to pierce for the button holes and to cut out the pattern. The film would be rendered porous by the electric piercing process which may occur either before or after the mechanical steps of piercing and/or embossing, but which preferably precedes such a mechanical step or steps. One reason for first electrically piercing the film is that in the subsequent mechanical piercing or embossing the heat will smooth off any rough edges left by the electric spark, thus insuring against subsequent tears starting at such ragged edges or points. The spark can be quenched by creating an inert atmosphere around the sparking area or flooding with or immersing in a non-conducting fluid. The shirt can then be joined together over the shoulders and collar and sleeves attached, by fusing or otherwise.

The plastic material. of which the fabric is made can be of a solid color or can be variegated by feeding different colored plastic to different portions across the metal band.

Extruded strips can be deposited on the film for producing simulated seams or for ornamental effects and may be in contrasting colors.

In the operation of the process the fabric will be under at least enough tension to hold it taut. Now when the fabric is pierced by a spark or by a heated pin or cutter, the material will shrink away from the aperture due to its elasticity and to the melting of the material. The holes therefore have a burred rim at each side of the sheet, which strengthens the material about the holes. Usually, though not necessarily, the holes will occur in more or less staggered arrangement lengthwise of the sheet, and the elasticity of the sheet will thus be increased both lengthwise and crosswise.

For most purposes thermoplastic sheets will be the preferred material for application of my process, so that the sheet material can subsequently be shaped by the use of heat and also because the material is melted at the perforation, instead of having a hole burned through it by the spark or by a heated needle. But the method may also be used with thermosetting materials, according to the use to be made.

The figure is an elevation, partly in section, of an apparatus for performing the claimed process.

This process may be carried out by the use of various machines such as the following which will be the subjects of one or more patent applications yet to be filed: If the operation is to be performed on a flat sheet of material, a rotating cylinder carrying a raised helical blade can be mounted to rotate over a coacting stationary blade, so that a series of sparks will be produced approximately at right angles to the movement of the material. This will produce a series of uniformly spaced sparks across the entire width of material being acted upon.

A non-conducting fluid may be sprayed or flowed on the helical blade or the entire machine may be immersed in a fluid bath and this fluid may be inert gas or a non-conducting liquid such as transformer oil or the like.

A pattern cylinder carrying a raised design of conductive material may be rotated in timed relation with the movement of the material over the aforementioned stationary blade. A third rotating cylinder also carrying a helical blade will be arranged to coact with the rotating pattern cylinder so that sparking will occur between the pattern cylinder and its coacting helical blade when a high point of' the pattern comes into operative relation to the helical blade on the coacting cylinder. At such times there Will be no spark through the material, the pattern cylinder and the stationary blade being electrically connected, and the two helical blades being electrically connected.

Furthermore, these perforations can be produced by wrapping or forming a sheet of thermoplastic material about a conducting cylinder. This cylinder is mounted adjacent a laterally movable point, the cylinder and point serving as electrodes to cause sparks to pass through said" material. In timed relation to the aforesaid cylinder there may be a pattern cylinder which has a raised design embossed upon it and which has a coacting' electrode. Each cylinder is the ground connectionfor the same electric circuit and the electrodes are connected to form the other side of a circuit. The arrangement is such that normally perforations are made in they sheet about the conducting cylinder, but when a portion of the pattern operatively engages the electrode at the pattern cylinder the current to the conducting cylinder is interrupted and no perforations are made in the sheet.

In the production of sparks for perforating the material on a. formed mold, one or more insulated fingers, each carrying an electrode, would be caused to move over the material and follow its contour.

The electric sparks produce minute perforations of practically insensible size, whereas the mechanical piercing means produces visible perforations or holes. Therefore, I refer to a fabric that has been acted on by electric spark producing means as a porous fabric, whereas one having visible holes is herein denominated a perforated fabric.

When it is desirable to space the holes in the fabric closely together, it' may be necessary to immerse the spark producing mechanism in a bath of oil, such as transformer oil, or in a bath of some other fluid, having a higher dielectric strength than the material that is being pierced. For instance, nylon has a higher dielectric strength than air. But if the spark producing area is flooded with insulating oil or is immersed in a bath of insulating oil or-other suitable material, the sparks can be produced very close together, and thus a fabric can be produced with minute, closely-spaced perforations, and the sparks will penetrate the film much more readily than the insulating fluid.

This oil, or other insulating material can be sprayed or flowed onto the material, or the entire operating mechanism can be immersed in an oil bath.

While the term oil is used for description, it is intended to include any fluid insulating material which could be used for quenching the spark, or producing an insulation adjacent to the spark gap, various materials of such quality being known to those skilled in, the electric arts.

In the practice of that form of my invention wherein an insulating liquid is used all sparks w-ill ordinarily be produced under the surface of the oil or the like and thus the fire hazard will not occur. Should it be deemed advisable at any time to use an inflammable oil the entire mechanism may be immersed in an inert atmosphere, or so much of it as is found necessary.

In the illustrative apparatus shown in the drawings, reference character I 0 indicates a tank containing an insulating liquid I I, which may be any suitable oil or mixture of oils, silicones, or even compound gas, within the scope of the invention. A rotarydrum or form 12 is suitably mounted and driven as to move a film through the liquid or fluid H, as indicated at 13. This form is made of electrically conductive material, and there is mounted adjacent the same an electrode consisting of one or more points or prongs arranged close to the moving film, the electrode being shown at M and being insulated as indicated at 15. For maintaining the liquid in condition I preferably connect a filter i to the'bottom of the tank, the filter being in turn con nected to a pump for circulating the liquid through a pipe H3 and back to the tank by Way of a pipe [9.

It will be obvious to those skilled in the art that many changes may be made in the inventions herein disclosed; and therefore I do not limit myself to' what is described in the specification, but only" as indicated in the appended claim.

This application is a continuation-in-part of my application No. 677,519, dated June 18, 1946, now abandoned.

Having thus fully described my invention, what I claim is:

A method of perforating in a desired pattern a sheet of material having a dielectric constant hi -her than air, comprising the steps of enveloping a portion of the sheet in a fluid having a dielectric constant higher than that of air and the sheet, and producing electric spark discharges at intervals through said portion of the sheet.

HERBERT W. BEALL.

REFERENCES CITED The following references are of record in the file of this. patent:

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